Protective cover for sanding machines



May 16, 1967 M. H. PREVETTE PROTECTIVE COVER FOR SANDING MACHINES FiledSept. 15, 1965 2 Sheets-Sheet 1 INVENTQR MELVIN H. PREVETTE ATTORNEY May16, 1967 M. H. PREVETTE PROTECTIVE COVER FOR SANDING MACHINES 2Sheets-Sheet 2 Filed Sept. 13, 1965 FIG. 3

FIG. 4

INVENTOR MELVIN H. PREVETTE ATTORNEY United States Fatent G 3,319,636HRGTEJTTVE CGVER FUR SANIBih-lt IyiACI-HNES lVIeivin I i. Prevette,Lexington, N.., assignor to Lexington Abrasive Belts, incorporated,Lexington, N.C., a corporation of North Carolina Filed Sept. 13, 1965,Ser. No. 436,679 Claims. (Cl. 150-52) This invention relates toprotective covers for sanding machines, and more particularly to thattype of cover adapted to be positioned between an ex-pansible pneumatictube of a sanding machine and the abrasive sleeve which contacts thework.

Covers of this type have been use-d for many years to protect thepneumatic tube and prolong its useful life. For the most part, suchprior art covers are formed from lengths of canvas which are formed intosleeves corresponding in diameter to the mean diameter of the pneumatictube with which each such sleeve is to be used. These canvas sleeves areformed by overlapping the end edges of a rectangular length of canvasand stitching the overlapped portions with several rows of stitches.

The completed sleeve is pulled axially over a deflated pneumatic tubeand tied in place by drawstrings at each end of the canvas cover. Afterthe canvas cover is in place, an abrasive belt is drawn axially over thetube and the canvas cover, after which the tube is inflated. Theabrasive sleeve is held in place on the sanding machine by frictionexerted through the radial expansion of the pneumatic tube. Toward thisend, the canvas cover must have sufficient capacity to stretch to bearfirmly against the non-stretchable abrasive sleeve and hold it in placeand against slipping.

The canvas cover of the prior art which are overlapped at their endportion have proven objectionable in that the overlapped portions createbumps which adversely interfere with the sanding operation, in that itmakes it difficult to obtain a smooth surface on the work piece.Moreover, the bump creates a high spot on the abrasive sleeve which ismore susceptible to wear than the rest of the abrasive belt and whichthereby shortens the useful life of the abrasive sleeve.

Another difficulty which has been found with the prior art canvas coversstitched along overlapped end edge portions is that care must be takento form puckers of an optimum size in the fabric between rows ofstitches in order to protect the stitches from abrasion in use. Thepuckering of material between rows of stitches is also useful in thatthe puckers permit uniform stretching of the bias-cut cover by enablingstretching of that portion of the fabric between the rows of stitchesunder pressure of the inflated pneumatic tube. The positioning ofpuckers between the rows of stitches is a time-consuming and ratherexpensive operation requiring a certain amount of skill, therebycontributing to the cost of the cover.

Recently, an attempt has been made to overcome the diilicultiesexperienced with the prior art canvas cover with overlapped stitched endportions through the use of a stretchable nylon cover made fromone-piece tubular fabric. While the nylon cover has the advantage ofbeing made in tubular form without bumps and has the advantage ofstretchability, it has proven objectionable in that difiiculty isencountered in drawing it axially on the pneumatic tube. Much more timeis required in placing a stretchable nylon cover on a pneumatic tubethan is the case with the canvas cover whose diameter more nearlycoincides with the diameter of the deflated tube. Another objectionfound in using the stretchable nylon cover is the tendency of the nyloncover to twist on the pneumatic tube and the tendency of the abrasivesleeve to slip in use when positioned about a nylon cover.

It is the primary object of this invention to overcome the foregoingobjections to the prior art covers known to applicant and to provide acover which combines the advantages of a smooth surface contoureliminating objectionable bumps and suflicient stretchability androughness to firmly engage the abrasive sleeve and hold it againstslipping in use.

It is another object of the invention to provide a cover for pneumaticsanders which is free of objectionable bumps and which may be installedon a pneumatic tube of a sander with a minimum amount of down time.

One of the major objections to the prior art cover is the ninety degreestraight splice. This makes it necessary for the work piece that isbeing sanded to meet the splice in a direct manner, causing wear on bothabrasive sleeve and canvas cover at this point. The new type covers havethirty-five degree to forty-five degree angle splices which allows thework piece to slide over easily, thus eliminating bump, longer life onboth cover and abrasive and gives a more desirable finish.

Some of the objects of the invention having been stated, other objectswill appear to those skilled in the art as the description proceeds whentaken in conjunction with the accompanying drawings, in which:

FIGURE 1 is a fragmentary view of one embodiment of the invention withparts broken away;

FIGURE 2 is a fragmentary longitudinal sectional view of the cover andabrasive belt assembled on an inflated pneumatic tube of a sandingmachine;

FIGURE 3 is an enlarged fragmentary transverse sectional view takensubstantially along the line 3-3 in FIGURE 2;

FIGURE 4 is a view similar to FIGURE 1 but illustrating a modified formof the invention;

FIGURE 5 is an enlarged transverse sectional view taken substantiallyalong the line 5-5 in FIGURE 4.

Referring more specifically to the drawings, a cover made in accordancewith the invention is indicated at 10 in FIGURES 1 through 3. The coverll) is made from a piece of canvas which has been cut on the bias intorectangular configuration. Opposite end edges of the canvas are cut atan angle and are parallel to each other as shown at 11 and 12 in FIGURE1 when brought together to form a tubular sleeve. v

The cover is hemmed as at 25 adjacent its side edges to define channels26 through which drawstrings or wires 27 are passed for securing thecover to an inflated tube of a pneumatic sanding drum. Although only oneis shown, it will be understood that drawstrings or wires 27 areprovided at each side edge of the cover.

According to the preferred form of the invention, the end edges ill and12 are brought together in a butt joint as most clearly seen at 13 inFIGURES l and 3. The end edges 11 and 12 are held in abutting relationby a strip of relatively thin tape 14 adhered to the inner surface ofthe cover lltl and extending coextensively with the butt joint 13between the sides of the cover.

The tape 14 is preferably a composite fabric made from fifty percentcotton and fifty percent nylon with the cotton extending lengthwise ofthe tape and with the tape'cut on the bias to impart a modulus ofelasticity to the tape at least equal to that of the cover. The nylonextends widthwise of the tape for added strength. As most clearly seenin FIGURE 3, the gauge or thickness of the tape is only a fraction ofthe gauge or thickness of the canvas cover. The relatively thin tape 14is compressed within the body of the relatively thick canvas cover 16,and as shown in FIGURE 3, the thickness of the tape 14 is insufficientto adversely affect the uniformly smooth upper surface of the canvascover 10 in use.

In FIGURE 2 the cover is shown installed on a pneumatic sanding drum.The sanding drum comprises an inflatable tube secured to end plates 16,only one of which is shown and held in place by a mounting ring 17. Theend plates 16 are journalled on a rotatable shaft 18 which may be drivenby a suitable mechanism, not shown. An air valve 19 providescommunication between the atmosphere and the interior of the tube 15whereby compressed air may be selectively introduced into and removedfrom the interior of the tube 15 to inflate it after the cover 10 andabrasive sleeve 20 have been mounted as shown in FIGURE 2.

Mounted as shown in FIGURE 2, the abrasive sleeve 20 is frictionallyheld against movement relative to the tube 15 even under pressure of awork piece, not shown, by the canvas cover 10 which has stretched underpressure of the inflated tube 15. The cover It), being cut on the bias,has an inherent modulus of elasticity and consequent capacity to stretchin a direction between the end edges 11 and 12. Although limited, thisinherent elasticity is to permit the canvas cover to conform to theshape of the inflated tube 15 as shown in FIGURE 2 and thereby bearagainst the inner surface of the relatively non-stretchable abrasivesleeve 20.

The tape 14 may be adhered to the inner surface of the cover 10 alongthe butt joint 13 with any suitable adhesive. Adhesives which have beenfound satisfactory for this purpose must have the inherent ability tostretch to the extent required by inflation of the tube 15 and toretract without losing its adherence when the tube 15 is deflated. Theadhesive must also be capable of withstanding the pressures exerted bythe work piece which further stretch the cover 10, the tape 14 and theadhesive, not shown. One adhesive which has been found suitable for usewith the invention is sold by United Shoe Machinery Corporation underthe designation Bostic 7070. It has been found preferable to combinefive parts of Bostic 7070 with one part of Boscoater No. 2, also sold byUnited Shoe Machinery Corporation.

An essential element of this invention is that the abutting edges 11 and12 be secured together in a manner that does not adversely affect theuniformly smooth upper surface of the cover 10 and at the same timepreserving the inherent stretchability of the fabric from which thecover 10 is made adjacent the butt joint 13.

The form of invention shown in FIGURES 4 and 5 is generally .similar tothat shown in FIGURES 13, and differs from that just described only inthat the end edges of the cover are adhesively secured together withouta tape. Instead, the overlapping end portions 11 and 12 are secureddirectly together by a suitable adhesive which may be the same as thatdescribed in connection with the first form of the invention andindicated at 21 in FIG- URE 5.

While the overlapped joint 22 does result in the end edge 12 beingslightly above the plane of the upper surface of the cover 10, it hasbeen found in practice that this does not create an objectionable bumpor adversely interfere with the uniformly smooth upper surface of thecover 10. This surprising result is believed to be attributable to thereduced thickness obtained by elimination of the need for puckering theupper layer of the overlapped end portions in the fabric as hadpreviously been the practice in the prior art cover in which theoverlapped end portions were sewn together by thread. According to thepresent invention sufficient stretchability is imparted to theoverlapped joint 22 by the stretchable and retractable adhesive 21without need for unduly thickening the overlapped joint by puckering thefabric as has previously been required in order to achieve the desiredstretchability at the joint in the prior art covers. In practicing bothforms of the invention care is to be taken that the area immediatelyadjacent the joint is not undesirably stiffened. It is a characteristicof this invention that the inherent capacity of the cover to stretch ina direction between its end edges 11 and 12 is not impaired by theadhesive used to form the joint. This is the reason for selecting anadhesive characterized by its capacity to stretch. Otherwise, the areaadjacent the joint would be undesirably stiffened and thereby offergreater resistance than the remaining portions of the cover to theapplication of inward pressure by the work piece against the abrasivesleeve during a sanding operation. Such a stiffened area would beundesirable because it would be, in effect, a bump in use which wouldhasten the deterioration of the abrasive sleeve and also adverselyaffect the smoothness of the sanding operation.

It will be appreciated by those skilled in the art that the coveraccording to either form of the invention may be made in any desiredsize and shape to snugly conform to the configuration of the pneumatictube in connection with which the cover is intended to be used.

There is thus provided an improved cover with characteristics of optimumstretchability and smoothness for efficient protection of a pneumatictube and retention of the abrasive sleeve on the tube in use.

In the drawings and specification there have been set forth preferredembodiments of the invention and although specific terms are employed,they are used in a generic and descriptive sense only and not forpurposes of limitation, the scope of the invention being defined in theclaims.

I claim: 7

1. A cover for pneumatic tube sanding machines com prising a rectangularpiece of canvas cut on the bias and having opposite end edges cut at anangle in parallel relation to each other, and an elastic adhesiveadhering the said end edges in adjoining relation, the joint defined bythe adjoining end edges being of substantially the same modulus ofelasticity as the remainder of said cover.

2. A protective covering for pneumatic sanding drums of the type havingan inflatable tube adapted to support an abrasive sleeve, said covercomprising a rectangular piece of canvas cut on the bias and having endedges and side edges, means adjacent said side edges for retaining thecover on the tube, said cover having a substantially uniform moduluselasticity between its end edges, and means adhesively securing said endedges together without adversely increasing the thickness of the coverat the joint and while preserving the same modulus of elasticityadjacent the end edges as exists throughout the remainder of the cover.

3. A cover according to claim 2 wherein said end edges abut one anotherto form a butt joint, and wherein said means for adhesively securingtogether the end edges comprises a length of tape adhesively secured tothe end edges and overlying the butt joint, and a layer of adhesivebetween the tape and the cover, said adhesive being characterized by itscapacity to stretch and retract to the same degree as said cover.

4. A cover according to claim 3 wherein said tape is stretchable in thesame direction as said cover and to at least the same degree as saidcover.

5. A cover according to claim 3 wherein said tape is formed from nylonyarns in one direction and from cotton yarns in the other direction andis cut on the bias to impart a measure of stretchability to the tapecorresponding to the stretchability in said cover between its end edges.

References Cited by the Examiner UNITED STATES PATENTS 206,976 8/1878Sands -52 767,767 8/1904 Ruegg 15052 2,225,073 12/1940 Miller 51-3732,796,700 6/1957 Katz 4731 FOREIGN PATENTS 649,558 1/1951 Great Britain.978,459 12/1964 Great Britain.

FRANKLIN T. GARRETT, Primary Examiner.

1. A COVER FOR PNEUMATIC TUBE SANDING MACHINES COMPRISING A RECTANGULARPIECE OF CANVAS CUT ON THE BIAS AND HAVING OPPOSITE END EDGES CUT AT ANANGLE IN PARALLEL RELATION TO EACH OTHER, AND AN ELASTIC ADHESIVEADHERING THE SAID END EDGES IN ADJOINING RELATION, THE JOINT DEFINED BYTHE ADJOINING END EDGES BEING OF SUBSTANTIALLY THE SAME MODULUS OFELASTICITY AS THE REMAINDER OF SAID COVER.